Power supply systems are pervasive in many electronic applications from computers to automobiles. Generally, voltages within a power supply system are produced by performing a DC-DC, a DC-AC, and/or an AC-DC conversion by operating a switch loaded with an inductor or transformer. DC-DC converters, such as buck converters, are used in systems that use multiple power supplies. For example, in an automotive system, a microcontroller that nominally operates at a 5V power supply voltage may use a buck converter to produce a local 5V power supply from the 12V car battery. Such a buck converter can be operated by driving an inductor using a high-side switching transistor coupled to a DC power supply. The output voltage of the buck converter can be controlled by varying the pulse-width of the time during which the switching transistor is in a conductive state.
In some buck converter implementations, the switching transistor is a discrete switching transistor driven by a switch driver integrated circuit, or is included on an integrated circuit that includes both the switch driver and the switching transistor. Because a high side driver is often referenced to a high voltage, some switch driver circuits use level shifters and bootstrap capacitors in order to drive the gate of the switching transistor with a voltage level sufficient to turn-on or turn-off the device.
Switching power supplies are generally more efficient than other power supply technologies, such as linear voltage regulators, but they are still prone to some inefficiencies. These inefficiencies can be caused by excess power consumed by switching power losses in the switching transistor, driving losses incurred while driving the switching transistor, and conductive losses.